The demonstration that progenitor cells in regions of the adult mammalian brain such as the dentate gyrus of the hippocampus can undergo mitosis and generate new cells that differentiate into functionally integrated neurons throughout life has marked a new era in neuroscience. In recent years, a wide range of investigations has been directed at understanding the physiological mechanisms and functional relevance of this form of brain plasticity. Our current knowledge of adult hippocampal neurogenesis indicates that the production of new cells in the brain follows a multi-step process during which newborn cells are submitted to various regulatory factors that influence cell proliferation, maturation, fate determination and survival. As details of the dynamics of morphological maturation and functional integration of newborn neurons in corticohippocampal circuits have become clearer, an increasing number of studies have examined how environmental and/or behavioural factors can modulate neurogenesis and affect hippocampal-dependent learning and memory. In this article we present an overview of recent literature that relates neurogenesis to hippo-